Scour Around Porous and Solid Structures: Sediment Transport, Porosity Effects, and Semi-Theoretical Scour Evolution Model

A high-fidelity 3D computational model, ibScourFoam, was employed to investigate sediment transport and scour around solid and porous hydraulic structures, specifically focusing on the differences induced by structural porosity. The model integrated an immersed-boundary approach to simulate the erodible bed, allowing for the first time to perform a detailed analysis of the scour process. By examining the wall shear stress distribution and statistics, and bathymetry at various stages of morphological evolution, this study found significant differences in scour patterns and depth between solid and porous structures. The findings revealed that porous structures reduce the intensity and variability of wall shear stress, leading to more stable and uniform flow within the scour hole. A new semi-theoretical model was developed to predict the temporal evolution of scour depth based on a shear decay function, incorporating porosity as a key factor. In contrast to previous pure empirical models, the new model incorporates more physics and fully utilizes the detailed flow information previously unavailable, and thus is more generalizable. This research provides valuable insights and tools for the design and analysis of hydraulic structures in river restoration and management.